1. Field of the Invention
The subject invention generally pertains to PTAC refrigerant systems such as those commonly used for hotel rooms. The invention more specifically pertains to a way of selectively configuring the system for local or remote control.
2. Description of Related Art
Packaged Terminal Air Conditioners/Heat Pumps or PTACs, as they are known in the HVAC industry, are self-contained refrigerant systems often used for cooling and heating hotel rooms; however, they are also used in a variety of other commercial and residential applications such as apartments, hospitals, nursing homes, schools, and government buildings. PTACs are usually installed in an opening of a building's outer wall, so an exterior-facing refrigerant coil can exchange heat with the outside air.
In warmer climates, PTACs might only be used for cooling. In cooler climates, however, the refrigerant side of the system may be a heat pump for heating or cooling. PTACs may also include an electric heater if the refrigerant system lacks a heating mode or if the heat pump is unable to meet the heating demand of particularly cold days. PTAC's are also available with a hydronic (water/steam) heating option.
To control the temperature of a room, PTACs can be controlled in response to a temperature sensor that is usually installed in one of two locations. The temperature sensor can be installed within the PTAC's housing itself or in a thermostat mounted to a wall or some other remote location in the room. Both locations have their advantages and disadvantages.
Installing the sensor within the PTAC's housing is usually less expensive and simplifies the installation of the system. In such a location, however, the sensor may not necessarily provide the best temperature reading, as the temperature is being sensed at the elevation and vicinity of where the heating or cooling is occurring rather than at the location of the occupants in the room. Moreover, since PTACs are usually mounted along an outside wall and usually beneath a window, the temperature of the outside air and sunshine through the window can affect the sensor.
A wall-mounted sensor, on the other hand, can be spaced apart from the window, outside wall, and PTAC housing, and it can be installed closer to the occupants. Thus, a wall-mounted sensor may provide a reading that more accurately represents the room's overall temperature. In the case of a hotel installation, a temperature sensor installed within a wall-mounted thermostat may resemble thermostats that room guests have in their own homes, which can provide the guests with a more familiar, home-like environment, rather than an impersonal hotel atmosphere. Wall-mounted thermostats, unfortunately, are generally more expensive to install due to behind-the-wall wiring that is normally run between the thermostat and the rest of the PTAC unit.
To avoid or minimize the cost of the added wiring, some remotely mounted thermostats communicate via a wireless communication link. Even so-called wireless wall-mounted thermostats, however, still need a power source, which may require behind-the-wall wiring or batteries. Batteries may eliminate the wiring but can be a nuisance to replace. Moreover, since some users still prefer the less expensive PTAC units with a built-in temperature sensor, it can be expensive for a PTAC manufacturer to provide and stock both types of PTAC units, i.e., those with and without remote temperature sensing.
Some manufactures provide thermostats that can be selectively mounted locally or remotely. With such systems, the temperature sensor is normally contained within the thermostat's housing, which may be fine if the thermostat is remotely mounted to a wall. If, on the other hand, the thermostat is installed where the heating or cooling occurs, the best location for the temperature sensor may be directly upstream of the system's heat exchanger, but that may be impossible if the temperature sensor is still contained and sheltered within the thermostat's housing.
Consequently, there is still a need for a practical and effective PTAC system whose thermostat can be selectively installed locally or remotely without sacrificing its ability to sense the air temperature at the best available location.